The DEA does have a process of approving scientific study of drugs but this isn't driven by scientific concerns it's driven by political concerns. This is especially a problem given that the DEA is run by law enforcement professionals not scientific professionals.
What is the wisdom in letting law enforcement professionals decide which drugs are legal and which are illegal? Shouldn't that be the job of the FDA?
But even then it would get mired up in politics. It might not be as bad as it is now but it would still be bad.
Legalizing all drugs would open up major opportunities for science and we would quickly understand a lot of things which if we knew about them now could for all we know have meant a cure for cancer or HIV.
For drugs that are truly dangerous make people take them and remain at special facilities for the duration of the high under the supervision of professionals. And if people want to sign up for a research study with informed consent they should be able to do that as well.
Prohibition doesn't work. The drug market can either be under the control of the black market or it can be under the control of a legal, regulated market.
Prohibition has never been logically consistent. Government proves itself over and over again incompetent to carry out such a task. One very dangerous drug, datura is completely legal. Read about it. I'd keep it legal but I'd have it restricted to those special facilities I mentioned above.
Outlawing drugs like marijuana censors science and takes away resources which could be used in a scientific or research setting and wastes them on law enforcement chasing petty criminals with an ounce or two. It also wastes money which could be used in research and development on court fees and prison upkeep for the criminals prosecuted under the drug laws.
Scientist usually have access to a wide variety of drugs and chemicals that the average citizen would not normally have. I do not thinking banning specific drugs will censor it because the science aspect of the community will stay have a means of using it to experiment and use it for medical reasons.